1. Technical Field
The present invention relates in general to static electricity discharge devices and is particularly directed to a system, device and method for automatically dissipating a static electricity charge from a surface.
2. Description of the Related Art
An undesirable aspect of aircraft (aerospace vehicle) flight is that the aircraft itself often suffers from an accumulation of electrostatic charges through various effects, including atmospheric conditions and the motion of the aircraft or parts thereof through the atmosphere. (A person of ordinary skill in the art will understand that the terms “aircraft” and “aerospace vehicle” can be used interchangeably throughout this application.) The accumulation of the electrostatic charges tends to build up potentials that can become dangerous and can cause, for example, radio frequency interference, electrical shock to persons connected with the aircraft, equipment failures and unwanted ignition of fuel and armament.
Aircraft can accumulate electrostatic charges for several reasons. For example, the atmosphere naturally carries a charge associated with the electrical field existing between the Earth and the ionosphere. This charge can be approximately 100,000 volts at a typical flying height of about 30,000 feet altitude. The low humidity present at a typical flying altitude can lead to the buildup of large electrostatic charges. An aircraft can acquire a charge of one million volts or more. This charge can be even higher for larger planes due to their increased size. Thus, an aircraft can build up static simply from its flight through the air. In addition, an aircraft can also accumulate charge while on the ground. This accumulation can occur due to dry air currents moving past the fuselage coupled with, for example, the aircraft sitting on an insulating/poor conducting surface.
In one specific example, an aircraft can accumulate charge when struck by lighting. If an aircraft is struck by lightning, the lightning initially attaches to an extremity, such as the nose or wing tip, and then moves to the fuselage. There, current can travel through the conductive exterior skin and structures of the aircraft fuselage. The current can then exit off some extremity, such as the tail or wheels. In addition, static dischargers can help remove charge from aircraft. Static discharge antennas, for example, are normally located on wing tips, rudder and elevator. These devices attempt to reduce the charge. However, such devices are primarily functional when the aircraft is in flight, as they have almost no effectiveness when the aircraft is on the ground. If the charge is not completely dissipated by the time the aircraft is ready for deplaning, a hazardous condition arises.
Thus, it is well known that the buildup of static electricity poses in-flight and ground based hazards. What is needed is a system and device that can automatically cause the discharge of static electricity from the fuselage of an aircraft before ground personnel or aircraft occupants come into contact with the skin. Such a system and device is also needed that can provide low cost static discharge and grounding systems. Such a system should be inexpensive to manufacture, install, operate and maintain. If such a system were available, it would result in cost-savings in relation to damage to facilities. More importantly, to prevent risk of injury or death to ground personnel, or others, the greatest need is for safer ways to discharge static electricity from aircraft or other surfaces, as the hazards from the build up of electrostatic charge are extreme.